Seat back frame

ABSTRACT

Embodiments of the present invention may include a seat back frame of a vehicle seat. The vehicle seat has a seat back main body configured to support the back of an occupant and an extension portion extending from a side of the seat back main body. The seat back frame has a main body frame, an extension frame, and a connection member. 
     The main body frame may form a framework of the seat back main body and may be mounted on a base. The extension frame may form a framework of the extension portion. The connection member connects the extension frame to a side of the main body frame. The connection member has a rear support portion and a front support portion. The rear support portion contacts the main body frame and the extension frame from the rear so that the rear support portion integrally couples the main body frame and the extension frame. The front support portion contacts with the main body frame and the extension frame from the front so that the front support portion can couple the main body frame and the extension frame.

This application claims priority to Japanese patent application serialnumber 2012-140301, the contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a seat back frame of avehicle seat.

2. Description of the Related Art

The vehicle seat has a seat back. A seat back described in JapaneseLaid-Open Patent Publication 2008-194289 has a seat back main bodyadapted to support a back of an occupant, and an extension portionextending from a side of the seat back main body. The seat back mainbody has a main body frame having high structural strength and it'spreferably fixed onto a floor. The extension portion has an extensionframe supported on the side of the main body frame in a cantilever-likemanner. The extension frame and the main body frame each have a circularpipe, and the extension frame and the main body frame are connected toeach other by a connection structure. The connection structure has asteel bracket that connects the circular pipes. The bracket extendsbehind the circular pipes to contact rear sides of the circular pipes.While the connection structure may be resistant to forces approachingthe extension portion from the front, it is vulnerable to forcesapproaching from the rear.

Therefore, there is a need in the art for a seat back frame that has anextension portion with high structural strength.

SUMMARY OF THE INVENTION

According to an aspect of the invention, certain embodiments of thepresent invention include a seat back frame of a vehicle seat. Thevehicle seat has a seat back main body configured to support a back ofan occupant and an extension portion extending from a side of the seatback main body. The seat back frame has a main body frame, an extensionframe, and a connection member. The main body frame may form a frameworkfor the seat back main body and may be mounted on a base. The extensionframe may form a framework of the extension portion. The connectionmember connects the extension frame to a side of the main body frame.The seat back frame further has a rear support portion and a frontsupport portion. The rear support portion contacts the main body frameand the extension frame from the rear so that the rear support portionintegrally couples the main body frame with the extension frame. Thefront support portion contacts the main body frame and the extensionframe from the front so that the front support portion integrallycouples the main body frame to the extension frame.

Thus, the extension frame is supported and connected from both the frontand rear sides with respect to the main body frame. Thereby, the seatback frame can have a connection structure that is resistant to forcescoming from both the front and the rear. The strength of the extensionportion can be increased by the connection structure.

In another aspect of the invention, the rear and front support portionsmay be provided at different heights. In this configuration, a bentportion or a protrusion portion extending in a front-back direction maybe used for the rear and front support portions so that they won'tinterfere with each other. Thus, it is possible to reduce the thicknessin the front-back direction of the seat back frame.

In another aspect of the invention the rear support portion may beconfigured so as to connect an upper portion of the main body frame andan upper portion of the extension frame. The front support portion maybe configured so as to connect an intermediate portion of the main bodyframe and an intermediate portion of the extension frame. Force comingfrom the front side of the seat may be transferred to the extensionportion. This force may then be substantially transferred at a locationfrom the front support portion to the seat back main body. This locationof transfer may be lower than the position of a rear support portion. Inthis way, the structural strength of the extension portion can beeffectively increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a seat with a seat back frame of oneaspect of the present invention;

FIG. 2 is a perspective view of the seat back frame;

FIG. 3 is a rear view of the seat back frame; and

FIG. 4 is an enlarged perspective view of a main portion of the seatback frame shown from behind.

DETAILED DESCRIPTION OF THE INVENTION

Each of the additional features and teachings disclosed above and belowmay be utilized separately or in conjunction with other features andteachings to provide improved seat back frames. Representative examplesof the present invention, which utilize many of these additionalfeatures and teachings both separately and in conjunction with oneanother, will now be described in detail with reference to the attacheddrawings. This detailed description is merely intended to teach a personof ordinary skill in the art further details for practicing preferredaspects of the present teachings and is not intended to limit the scopeof the invention. Only the claims define the scope of the claimedinvention. Therefore, combinations of features and steps disclosed inthe following detailed description may not be necessary to practice theinvention in the broadest sense, and are instead taught merely toparticularly describe representative examples of the invention.Moreover, various features of the representative examples and thedependent claims may be combined in ways that are not specificallyenumerated in order to provide additional useful configurations of thepresent teachings.

A vehicle seat 1 shown in FIG. 1 is a driver's seat of a vehicle. Thevehicle seat 1 has a seat back 2 that supports a back of an occupantsitting on the vehicle seat 1, a seat cushion 3 on which the occupantsits, and a headrest 4 that supports a head of the occupant. The seatback 2 has a seat back frame 10.

The seat back 2 has a seat back main body 2A that supports the back ofthe occupant, and an extension portion 2B that extends to the inside ofthe vehicle (a right side as shown in FIG. 1) from the seat back mainbody 2A. The extension portion 2B extends laterally from the seat backmain body 2A. The extension portion 2B preferably has a surface locatedon the same plane as a surface of the seat back main body 2A, and a backsurface located on the same plane as a back surface of the seat backmain body 2A. The extension portion 2B preferably has the same sideshape as a side shape of the seat back main body 2A. That is to say, theshape of a projection side of the extension portion 2B may besubstantially the same as the shape of a projection side of the seatback main body 2A. A seat back of a passenger seat (not shown) islocated near the lateral side of the seat back main body 2A. Theextension portion 2B is able to connect the seat back main body 2A andthe seat back of the passenger seat.

The seat back main body 2A and the seat cushion 3 may be connected toeach other by a disk-shaped reclining device 5. The reclining device 5is a rotary shaft device that can connect the two members such that theycan rotate and/or be arranged in a fixed manner. The reclining device 5connects the lower end portions of both the left and right sides of theseat back main body 2A and the rear end portions of both the left andright sides of the seat cushion 3. The reclining device 5 connects thelower end portions of both side frames 11 of the seat back main body 2Aand the rear end portions of both side frames 3A of the seat cushion 3.Thereby, a backrest angle of the seat back 2 relative to the seatcushion 3 can be adjusted.

Each of the reclining devices 5 is usually maintained in a locked statewhereby they fix the backrest angle of the seat back 2. A release lever5C is provided on an outer side (a left side in a show direction) of theseat cushion 3. When the release lever 5C is pulled up, the recliningdevice 5 is unlocked. The reclining device 5 has an operation shaft 5Ainserted into the center thereof. The operation shafts 5A of a pair ofreclining devices 5 are connected by a connecting rod 5B and can berotated. When the release lever 5C is pulled up, the operation shaft 5Alocated on an outer side is rotated in the release operation direction.The operation shaft 5A of the inner side is also rotated in the releaseoperation direction at the same time. In this way, both of the recliningdevices 5 can be unlocked at the same time.

Each of the reclining devices 5 switches from a locked state to anunlocked state whereby the backrest angle of the seat back 2 can befreely changed in the front-back direction. After changing the backrestangle of the seat back 2 to a predetermined angle, the operation of therelease lever 5C can be stopped. Thereby, each of the reclining devices5 returns to the locked state again, and the backrest angle of the seatback 2 is fixed at the predetermined angle. The reclining device 5 canhave the same configuration as that disclosed in the document ofJapanese Laid-Open Patent Publication 2011-116303 or the like.

Between the left and right portions of the seat back 2 and the left andright portions of the seat cushion 3, a spiral spring 6 is providedwhich typically biases the seat back 2 forward. When the fixation of thebackrest angle of the seat back 2 is released, the seat back 2 rotateswhereby it may come into contact with the back of the occupant via thebiasing force of the spiral spring 6. When the back of the occupant istilted forwards or backwards, the backrest angle of the seat back 2 ischanged in accordance with the tilting of the back. In this way, thebackrest angle of the seat back 2 can be easily adjusted.

The seat cushion 3 may be provided on a floor of a vehicle using leftand right slide devices (not shown). The position of the seat cushion 3can be adjusted with respect to the floor in the front-back direction.The slide device can have, for example, a structure disclosed in thedocument of Japanese Laid-Open Patent Publication 2010-221935 or thelike. The seat back 2 may have an extension portion 2B. The seat cushion3 may have an extension portion 3B extending the seat width direction inaccordance with the extension portion 2B. On the upper surface of theextension portion 3B, a recessed cup holder 3C may be formed in which adrink or a small object can be placed.

The headrest 4 is typically mounted above the seat back 2. The headrest4 preferably has two rod-like stays (not shown) protruding downward fromthe headrest main body. The seat back frame 10 of the seat back 2 has anupper frame 12. The two square tube-shaped holders 15 may be fixed tothe upper frame 12. A support member may be mounted inside each of theholders 15. The stays may be inserted into the support members, and theheadrest 4 may be fixed to the upper portion of the seat back 2. Themounting structure, which mounts the headrest 4 to the seat back 2, canhave a structure, for example, disclosed in Japanese Laid-Open PatentPublication 2008-239075.

As shown in FIGS. 1 and 2, the seat back frame 10 has a main body frame10A, an extension frame 10B, and a connection member 16. The main bodyframe 10A forms a a framework of the seat back main body 2A. Theextension frame 10B forms a framework of the extension portion 2B. Theconnection member 16 connects the extension frame 10B to the main bodyframe 10A.

The main body frame 10A has side frames 11, upper frame 12, holders 15,an upper reinforcement plate 13, and a lower reinforcement plate 14. Thecomponents are integrally assembled. The side frame 11 has a pair ofvertical left and right plates. The upper frame 12 is an inverseU-shaped pipe that connects the upper end portions of the side frames11. The holder 15 has a square tube shape, and is provided on the leftand right portions of the upper frame 12. The upper reinforcement plate13 has a horizontal plate between the left and right leg portions of theupper frame 12. The lower reinforcement plate 14 has a horizontal platebetween the lower portions of the side frames 11.

When manufacturing the side frame 11, a steel plate material is cut in avertically long shape using a press. Next, the front and rear edgeportions of the steel plate material are bent to the inside of the seatin a flange shape. Each of the bent edge portions is able to increasestrength resistant to bending or distortion of the side frame 11. Eachof the edge portions suppresses the protrusion of the side frame 11 tothe outside (the front and the rear or the outside of the seat). Theside frame 11 is located on the side of the seat back main body 2A, andforms the framework of both of left and right sides of the seat backmain body 2A. Both of the side frames 11 have the surfaces facing eachother in the seat width direction.

When manufacturing the upper frame 12, a circular steel pipe istypically cut to a predetermined length using a press. Next, thecircular steel pipe material is bent in an inverse U shape. The upperframe 12 has left and right leg portions extending downward, and both ofthe leg portions are welded to the upper end portion of each of the sideframes 11. In this way, the upper frame 12 can be coupled to the sideframe 11.

The upper end portion of the side frame 11 is bent in a semi-cylindricalshape so that the shape thereof is matched with the outercircumferential surface of each leg portion of the upper frame 12.Thereby, each leg portion of the upper frame 12 can contact with eachupper end portion of each side frame 11 in a wide area. They aretypically can be welded in a wide area and coupled to each other.

The holder 15 is manufactured by cutting a squared-off steel pipe to apredetermined length. The holder 15 extends vertically. The upperportion of the holder 15 is connected to a front surface of a centralportion extending in the seat width direction of the upper frame 12. Thelower portion of the holder 15 is connected to a front surface of theupper reinforcement plate 13 by the welding. The holder 15 can supportthe headrest 4 (see FIG. 1) due to its high structural strength. It usesthe upper frame 12 and the upper reinforcement plate 13 for support.

When manufacturing the upper reinforcement plate 13, a sheet of steelmaterial is cut using a press. Next, the upper and lower edge portionsof the steel material are bent to the front of the seat in a flangeshape. The upper and lower bent edge portions can increase strengthresistance to bending or distortion. The upper and lower edge portionscan suppress the angulation of the upper reinforcement plate 13 to theoutside (the rear side of the seat). The left and right end portions ofthe upper reinforcement plate 13 are welded to the rear surfaces of eachleg portion of the upper frame 12. In this way, the upper reinforcementplate 13 can be fixed and integrally coupled to both leg portions of theupper frame 12. Each end portion of the upper reinforcement plate 13 isbent in a semi-cylindrical shape that is matched with the outercircumferential surface of the leg portions of the upper frame 12.Thereby, each end portion of the upper reinforcement plate 13 cancontact each leg portion of the upper frame 12. They are preferablywelded and coupled to each other.

In manufacturing the lower reinforcement plate 14, a sheet of steel iscut using a press. Next, the upper and lower edge portions of the steelplate material are bent to the front of the seat in a flange shape. Theupper and lower edge portions can increase strength resistant to bendingor distortion of the lower reinforcement plate 14. The upper and loweredge portions can suppress the angulation of the lower reinforcementplate 14 to the outside (the rear side of the seat). The left and rightend portions of the lower reinforcement plate 14 are welded to a frontsurface of the rear edge portion bend to the inside of the seat of thelower portion of the side frame 11. Thereby, the lower reinforcementplate 14 can be coupled to the lower portions of the side frames 11.

When manufacturing the extension frame 10B, in the same manner as theupper frame 12, a steel pipe is cut to a predetermined length. Next, thesteel pipe is bent in a U shape in the transverse direction. Theextension frame 10B is placed so that the U-shaped opening faces themain body frame 10A. The upper end portion 10B1 of the extension frame10B is coupled to a shoulder portion of the upper frame 12 of the mainbody frame 10A by a rear support member (portion) 16A of the connectionmember 16. A lower end portion 10B2 penetrates and is fitted to the sideframe 11 of the main body frame 10A, and is coupled to the side frame 11by welding.

The extension frame 10B has an intermediate portion 10B3 extendingvertically and downward from the upper end portion 10B1 to the lower endportion 10B2. The intermediate portion 10B3 is coupled to a leg portion(a portion 12B) of the upper frame 12 of the main body frame 10A by afront support member (portion) 16B of the connection member 16. One sideof the extension frame 10B is coupled to the main body frame 10A, andthe extension frame 10B is supported by the main body frame 10A. Theextension frame 10B is at least partially provided within the main bodyframe 10A, and extends from the main body frame 10A in the lateraldirection.

The lower end portion 10B2 of the extension frame 10B is fitted to acircular hole formed in the side frame 11 in the seat width direction,and is welded to the side frame 11. For that reason, the extension frame10B can be coupled to the main body frame 10A in a simple configuration.However, the upper end portion 10B1 of the extension frame 10B iscoupled to the upper frame 12, without being fitted to the through holeof the upper frame 12. For that reason, the extension frame 10B is notcoupled to the main body frame 10A in a simple configuration. The upperend portion 10B1 of the extension frame 10B is coupled to the shoulderportion of the upper frame 12 formed by bending of the circular steelpipe. They are preferably connected via the connection member 16. Theconnection member 16 fixedly and integrally couples the extension frame10B with the upper frame 12 through a relatively simple configuration,without lowering the structural strength of the main body frame 10A.

As shown in FIGS. 2 to 4, the connection member 16 has a rear supportmember 16A and a front support member 16B. The rear support member 16Ais a flat plate-shaped steel plate material. The rear support member 16Ais coupled to the rear surface of the upper end portion 10B1 of theextension frame 10B and the rear surface of the shoulder portion of theupper frame 12. The front support member 16B is a circular steel pipematerial. The front support member 16B is coupled to the front surfaceof the intermediate portion 10B3 of the extension frame 10B and thefront surface of the leg portion (the portion 12B) of the upper frame12. In this way, the rear support member 16A and the front supportmember 16B couple the extension frame 10B to the upper frame 12.

As shown in FIGS. 3 and 4, the rear support member 16A is coupled withthe rear surface of the upper end portion 10B1 of the extension frame10B and the rear surface of the first portion 12 A and the rear surfaceof the second portion 12B of the upper frame 12. The rear support member16A is coupled to each of three back surfaces through welding. The upperend portion 10B1 of the extension frame 10B extends in the seat widthdirection. The first portion 12A extends in the seat width direction ofthe shoulder portion of the upper frame 12. The second portion 12B isbent and extends downward from the first portion 12A.

The rear support member 16A is coupled to the rear surface of the secondportion 12B, and thus the rotation about the first portion 12A isrestricted. The rear support member 16A is coupled to the rear surfaceof the upper end portion 10B1 and the rear surface of the first portion12A. In this way, the rotation about the second portion 12B isrestricted. The rear support member 16A can be coupled to both the firstportion 12A and the second portion 12B.

The rear support member 16A is provided in the shoulder portion of theupper frame 12, and the upper end portion 10B1 of the extension frame10B is coupled to the rear support member 16A. Thus, the rear supportmember 16A is able to couple the extension frame 10B to the shoulderportion of the upper frame 12.

The rear support member 16A has a pair of semi-cylindrical upper edgeportions 16A1. One upper edge portion 16A1 contacts the first portion12A of the upper frame 12, and corresponds to an outer circumferentialsurface shape of the steel pipe of the first portion 12A. The otherupper edge portion 16A1 contacts the extension frame 10B, andcorresponds to the outer circumferential surface shape of the steel pipeof the extension frame 10B. Each of the upper edge portions 16A1 cancontact the first portion 12A and the extension frame 10B, and can bewelded to it. Thereby, the rear support member 16A can be coupled to thefirst portion 12A and the extension frame 10B.

The upper edge portions 16A1 has a semi-cylindrical shape that extendsfrom the rear of the frames to the front so as to be able to contact thefirst portion 12A of the upper frame 12 and the extension frame 10B. Inthis way, the rear support member 16A can contact the first portion 12Aand the extension frame 10B from both the front and the rear.

The front support member 16B is a steel pipe. Both end portions 16B1 ofthe front support member 16B have a crushed flat shape. The both endportions 16B1 contact the intermediate portion 10B3 of the extensionframe 10B and the second portion 12B of the upper frame 12 from thefront, and are welded thereto. In this way, the front support member 16Bis coupled to the extension frame 10B and the upper frame 12.

The front support member 16B has a central portion having a steelpipe-shape. The central portion extends in the seat width direction. Thecentral portion is perpendicular to the intermediate portion 10B3 of theextension frame 10B and the second portion 12B of the upper frame 12.The central portion is located in the front-back direction insubstantially the same manner as the intermediate portion 10B3 and thesecond portion 12B. Both end portions 16B1 of the front support member16B have a crushed and curved shape so as to correspond to the shapes ofthe front surfaces of the intermediate portion 10B3 and the secondportion 12B. Thereby, both end portions 16B1 can contact theintermediate portion 10B3 and the second portion 12B and be weldedthereto. Thereby, the front support member 16B is coupled to theintermediate portion 10B3 and the second portion 12B.

The front support member 16B is set to substantially the same height asthe upper reinforcement plate 13. The upper reinforcement plate 13 iswelded to the rear surface of both leg portions of the upper frame 12.The upper reinforcement plate 13 supports the main body frame 10A fromthe rear. The front support member 16B supports the extension frame 10Bfrom the front. Thus, the main body frame 10A and the extension frame10B are fixedly supported by each other, and thus are hard to deflect ortwist in the front-back direction.

The rear support member 16A and the front support member 16B support andconnect the extension frame 10B and the main body frame 10A from thefront-back direction. Thus, the extension frame 10B is resistant to theinput load from both sides of the front and back with respect to themain body frame 10A. For example, when the seat back 2 is stood up, theextension frame 10B can sufficiently resist forces that may betransmitted to the extension portion 2B from the front or the rear. Whenthe seat back 2 is brought down forward, the extension frame 10B cansufficiently resist forces that may be transmitted to the back surfaceof the extension portion 2B from above.

The rear support member 16A and the front support member 16B are locatedat different positions. For that reason, the rear support member 16A cancontact the upper edge portion 16A1 without interfering with the frontsupport member 16B. The front support member 16B can be placed at thefront-back position corresponding to the upper frame 12 and theextension frame 10B without interfering with the rear support member16A. Thus, the thickness in the front-back direction of the seat backframe 10 can be reduced.

The rear support member 16A is provided at the high position in whichthe shoulder portion of the upper frame 12 and the upper end portion10B1 of the extension frame 10B are connected to each other. The frontsupport member 16B is provided at the low position in which the secondportion 12B of the upper frame 12 and the intermediate portion 10B3 ofthe extension frame 10B are connected to each other. Thus, the loadapplied to the extension portion 2B from the seat front is transmittedto the seat back main body 2A by the front support member 16B at the lowposition compared to the rear support member 16A. Thus, the structuralstrength of the extension portion 2B can be effectively

While the embodiments of invention have been described with reference tospecific configurations, it will be apparent to those skilled in the artthat many alternatives, modifications and variations may be made withoutdeparting from the scope of the present invention. Accordingly,embodiments of the present invention are intended to embrace all suchalternatives, modifications and variations that may fall within thespirit and scope of the appended claims. For example, embodiments of thepresent invention should not be limited to the representativeconfigurations, but may be modified, for example, as described below.

The seat back frame may be applied to the seat back of the driver's seatas described above, and may be applied to the seat backs of other seats.The seat back frame may be applied to the seats of the vehicle such as acar, and may be applied to, for example, vehicles such as a railwayvehicle.

As described above, the extension portion can be located between theseats positioned adjacent to each other. The extension portion connectsthe seat backs of the seats so as to fill the space between the seatbacks. Alternatively or additionally, the extension portion may supportthe back of the occupant sitting in front of the extension portion.

The extension frame and the main body frame (the upper frame) each maybe the circular steel pipe as described above. Alternatively, theextension frame may be a steel pipe, a squared-off steel pipe or thelike.

The rear support member and the front support member may be configuredas described above and may have other structures. As described above,the rear support member and the front support member may be differentmembers. Alternatively, both the rear support portion (member) and thefront support portion (member) may be constructed as a single member.

The rear and front support members may be welded and coupled to the mainbody frame or the extension frame as described above. Alternatively, therear and front support members may be coupled to the main body frame orthe extension frame by a bolt, caulking or the like.

As described above, the rear and front support members may be set toheights different from each other. Alternatively, the rear and frontsupport members may be set at the same height.

The rear support member may be located above the front support member asdescribed above. Alternatively, the rear support member may be locatedbelow the front support member.

As described above, the main body frame of the seat back main body maybe connected to the seat cushion so as to be capable of reclining.Alternatively, the main body frame may be fixed to the seat cushion.Alternatively, the main body frame may be fixed to a base member fixedon the floor. Alternatively, the main body frame may be fixed to amember fixed on the floor or may be attached to the member capable forreclining.

As described above, the main body frame of the seat back main body maybe connected to the floor via the seat cushion 3. Alternatively, themain body frame may be directly connected to the floor (base).

As described above, the main body frame of the seat back main body isconnected to a base. The base may be floor described above, a sidepanel, a roof panel, a vehicle member, a part of a vehicle body, or thelike.

As described above, the seat back frame may comprise one rear supportmember and one front support member. Alternatively, the seat back framemay more than one rear support members and/or more than one frontsupport members. All of the rear support members may be provided at afirst height or first heights. All of the front support portions may beprovided at a second height or second heights. All of the second heightsmay be different heights from all of the first height or first heights.

As described above, the upper reinforcement plate 13 and the frontsupport member (portion) 16B may be the different members.Alternatively, the upper reinforcement plate 13 and the front supportmember (portion) 16B may be constructed by or formed of one member.

This invention claims:
 1. A seat back frame of a vehicle seat, thevehicle seat having a seat back main body configured to support a backof an occupant and an extension portion extending from a side of theseat back main body, the seat back frame comprising: a main body framemounted on a base to form a framework for the seat back main body; anextension frame forming a framework for the extension portion; aconnection member for connecting the extension frame to a side of themain body frame, a rear support portion contacting the main body frameand the extension frame from the rear in order to couple the main bodyframe to the extension frame, and a front support portion contacting themain body frame and the extension frame from the front in order tocouple the main body frame to the extension frame.
 2. The seat backframe of claim 1, wherein the rear and front support portions aredifferent members.
 3. The seat back frame of claim 1, wherein the rearand front support portions are provided at different heights from eachother.
 4. The seat back frame of claim 3, wherein the rear supportportion is configured so as to connect an upper portion of the main bodyframe and an upper portion of the extension frame, and wherein the frontsupport portion is configured so as to connect an intermediate portionof the main body frame and an intermediate portion of the extensionframe.
 5. The seat back frame of claim 1, wherein all of the one or morerear support portions are provided at a first height(s), and all of theone or more front support portions are provided at a second height(s),the second height(s) being different height(s) from the first height(s).6. The seat back frame of claim 1, wherein the rear support portion isconstructed of a plate, and wherein the front support portion isconstructed of a pipe.
 7. The seat back frame of claim 1, wherein themain body frame comprises an upper frame and a reinforcement plate,wherein the upper frame comprises left and right leg portions extendingvertically, wherein the reinforcement plate extends between the left andright leg portions, and wherein the reinforcement plate and the frontsupport portion are provided at the same height.
 8. The seat back frameof claim 7, wherein the reinforcement plate and the front supportportion are formed of one member.